Did you know that the word “wrought” is the old past tense of the verb to work.  As irregular past-tense forms in English have historically been phased out over long periods of time, wrought became worked. Wrought iron literally means Worked iron.  Wrought iron is rarely completely pure. It is a fibrous material with many strands of slag are mixed into the metal. These slag inclusions give it a "grain" like wood, and distinct look when etched. Also due to the slag, it has a fibrous look when broken or bent past its failure point.  The fibers of wrought iron gives it some interesting properties, however. Hammering a piece of wrought iron cold causes the fibers to become packed tighter, which makes the iron both brittle and hard. As wrought iron lacks the carbon content necessary for tempering, it is believed that cultures that never discovered how to make steel would cold work wrought iron tools in order to harden them.  Source of information:  Wikipedia.